The present application is based on and claims priority from Japanese Patent Application Hei 11-222445 filed on Aug. 5, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fuel shut-off safety device to be mounted in a fuel injection system for an internal combustion engine.
2. Description of the Related Art
In a pressure accumulation type fuel injection system, high pressure fuel is accumulated into a common-rail, a surge tank, or a pressure-accumulation pipe by a high pressure pump. Usually, a fuel shut-off device is provided in such a system to shut off fuel for safety if an abnormal operation of a fuel injection valve, such as excessive fuel discharge, is detected. U.S. Pat. No. 5,692,476 or PCT Application Hei 9-512325 discloses such a fuel shut-off device.
However, such a fuel shut-off device is expensive because it is made up of numerous complicated parts. Moreover, for such a fuel shut-off device it is difficult to change the operation characteristics so that it can be applied to a different engine.
A main object of the invention is to provide a simple, reliable and inexpensive safety device to be mounted in a fuel injection system for an internal combustion engine.
Another object of the invention is to provide a fuel shut-off safety device in which the operation conditions can be changed easily.
According to the invention, a fuel shut-off device for an internal combustion engine includes a cylindrical body having a fuel passage and a valve seat, a piston disposed to axially slide in the fuel passage and having a valve body to shut off the fuel passage when it is seated on the valve seat, and biasing means for biasing the piston to unseat valve body from the valve seat. The piston has a center bore connected to a fuel inlet of the cylindrical body and an aperture connecting the center bore and the fuel passage. Therefore, an excessive amount of fuel can be prevented from flowing into the fuel injectors by a simple and inexpensive fuel shut-off device.
In the fuel shut-off device, the biasing means may be a coil spring disposed around the valve body.
The fuel shut-off device may further include a gasket having a flange portion in contact with the cylindrical body at the fuel inlet and two sleeve portions having different lengths longitudinally extending from the flange portion in opposite directions so that any one of the sleeve portions can be fitted in the fuel passage.